Glucose monitoring, the DCCT and new technologies

This was the first large-scale study to show definitively the benefit of making efforts to keep blood glucose levels within tight limits. The results have had a significant effect on the directions of new diabetes management research.

The Diabetes Control and Complications Trial (DCCT) was a 10-year study involving 1,441 people with insulin-dependent diabetes throughout the United States and Canada. It compared the effects of two different levels of insulin monitoring and blood-glucose control on the development and progression of diabetic complications. The results that emerged were so clear that the study was stopped a year ahead of schedule in 1993. They proved that tight blood glucose control prevents or delays the onset of complications, and showed that even minor improvements in diabetes control go some way towards lessening the risk of complications, and are even worthwhile for those who already have complications. One important outcome in terms of research activity has been a renewed focus on matching patterns of insulin delivery to the body's own requirements rather than simply seeking convenient dosage schedules.

Some key results of the DCCT are worth summarizing. Eye disease (retinopathy) was the main complication researchers looked at but they also studied kidney, nerve and heart disease. Participants were between the ages of 13-39 years old, with no high blood pressure or high cholesterol levels.

The lowest incidence of complications was found among people receiving intensive treatment, who had average blood-glucose levels of 8.6 mMo/L and HbA1c levels of around 7%. People receiving conventional treatment averaged a blood glucose level of 12.8 mMo/L.

Those who had no signs of retinopathy at the start and received intensive treatment had a 76% reduced risk of developing retinopathy compared to chose in the conventional treatment group.

Among those who already had signs of eye disease, intensive treatment reduced the risk of significant retinopathy by 54%, severe retinopathy by 47% and laser treatment by 56%.

It took six months for peoples' HbA1c levels to improve in the intensive treatment group. After that, they remained lower than the conventional group for the rest of the study. Intensive treatment reduced the appearance of neuropathy (nerve disease) by 69% in the primary prevention group and 57% in the secondary intervention group.

The development of kidney disease was slowed among those who had early signs of the complication at the start and received intensive treatment.

The practical implications of the DCCT study results were, first and foremost, that tighter control of blood glucose levels, through more frequent monitoring, directly correlates with reduced risk of the pathologies associated with hyperglycemia. Moreover, close monitoring of blood glucose will also preempt the short-term potential for hypoglycemia. The end result is that, for patients to minimize the risk of both the long term complications – the pathologies –and the short-term hypoglycemia of diabetes, they must sustain a rigorous regimen of blood glucose monitoring that becomes burdensome for many patients. In the medium to long term, the answer to this burden may be provided by new technologies, now in development, for continuous blood-glucose monitoring, and controlling insulin administration so that physiological blood glucose levels can be continuously maintained, avoiding both short- and long-term complications without undue disease management demands placed on the diabetic patient.

Meanwhile, some of the newer antidiabetic drugs, particularly the thiazolidinediones and the new short-acting insulins, should enable patients to comply with the guidelines of the DCCT while minimizing the concomitant risks. Fast-acting insulin analogues should also help in this way.